The present invention relates generally to the non-invasive monitoring of plasma glucose levels by inducing localized sweating which produces a glucose-containing sweat sample.
The monitoring of plasma glucose levels in patients is of major importance in the field of medicine in terms of diagnosis, health maintenance, and management of disease. Typically, plasma constituents, such as glucose, are monitored by removing a blood sample from the patient and analyzing the blood sample. This involves an invasive procedure, such as finger pricking or entering a vein with a syringe to remove the blood. These invasive procedures can be painful and inconvenient, especially for a self-testing patient.
Non-invasive technology is employed in a number of medical contexts. Medical iontophoresis is a procedure whereby electric current is employed to transdermally mobilize ionic medicaments. Pharmacologic agents can thereby be introduced into the patient, without invasion of the patient. Non-invasive technology is also employed in the diagnosis of certain disease states. For example, it is well known that the sweat of a patient suffering from cystic fibrosis contains elevated levels of chloride. Medical iontophoresis is employed to pharmacologically stimulate a sweating response using a test patch containing a sweat-inducing agent. The test patch collects the sweat and is then used to provide sweat for analysis of the chloride level in the sweat sample. This technique is described in detail in the Lattin et al. U.S. Pat. No. 4,457,748. Thus, the nonsweating through iontophoresis allows for the diagnosis of cystic fibrosis through the analysis of the chloride level in a sweat sample.
However, there is presently no technology available for the non-invasive monitoring of plasma constituents, such as glucose. Eccrine sweat contains many compounds of interest, but there is typically no glucose present in a sample of eccrine sweat on the skin surface. Although glucose may present in the secretory coil of the eccrine sweat gland in equilibrium with plasma glucose levels, that glucose is depleted as the sweat moves to the skin surface.
Therefore, there is a continuing need for improved non-invasive technologies for monitoring important constituents present in the plasma of a patient.